CN 101635077 A discloses an anti-theft detection method for a road lamp cable wherein an investigation signal in the form of a variable frequency input current signal is injected into the road lamp cable and wherein output current signals and output voltage signals are to be measured for different frequencies of the input current signal and wherein resonance frequencies of road lamps are to be taken into account and wherein a number of actual road lamps needs to be known. This way, in a relatively complex manner, the road lamp cable can be monitored.
A cable system comprises a cable and one or more loads. In case the loads comprise rectifier circuits with inputs coupled to the cable and with outputs coupled to storage circuits, the storage circuits may have a relatively large impact on the investigation signal and may make it difficult or even impossible to use the investigation signal.